The invention relates to arrangements for forming strips of elongated generally rod-shaped fasteners suitable for use in pneumatic nail drivers and the like. (Such fasteners may generally include nails, screw-nails, screws, pins, studs, and the like; for simplicity, however, such fasteners will be referred to as "nails" throughout the remainder of the specification and claims without in any way limiting the coverage of the invention to such other types of fasteners.)
Such nail strips ideally exhibit a plurality of successive nails maintained in parallel, evenly-spaced relation by an extruded ribbon of plastic material that is molded around the successive nails.
In known arrangements of this type, a conveying apparatus such as a transfer wheel has a plurality of spaced grooves on its periphery for receiving and advancing in a first plane a succession of incoming nails to be incorporated in the finished nail strips. An elongated support member having a first bearing surface that extends over a first number of the successive grooves of the conveying device engages and closes the grooves for capturing the received nails therein. An extruder cooperating with the conveying device advances a plastic ribbon along the shafts of the advancing nails to be adhered thereto, and a molding arrangement disposed downstream of the adhering means and illustratively comprising a pair of cooperating rolls thereupon serves to mold the adhered ribbon about the captured nails to form the required nail strip.
One disadvantage of known arrangements of this type is caused by the unavoidable differences in diameters of the nail shafts captured in the conveying grooves, and/or differences in the depths of the grooves themselves, whereby certain of the nail shafts protrude different distances out of the grooves. The pressure of the elongated support member on the nail shafts along the plurality of grooves contacted thereby will be uneven and will be greatest on the nail shafts protruding farthest beyond the grooves. As a result, the remaining nails then contacted by the support member will be free to move within the grooves during the advancing operation, notwithstanding that such nails remain captured in their respective grooves. The resulting movement of the nails within the grooves as such nails approach the molding portion of the assembly results in a situation where the finished nail strip will have its constituent nails randomly aligned therein.
As a result, when such misaligned nail strips are loaded into magazines to be ultimately introduced into pneumatic nail drivers or other suitable utilization apparatus, they serve to cause jamming and similar malfunctions of such apparatus.